DEV: Modernization and fixes

[keegangeorge]

This PR applies a few modernizations, fixes, and a small feature:

• Converts modal to .gjs
• Fixes regression where the incorrect class was used in the .scss causing styling not to be applied
• Updates css based on new changes to plugin outlet locations component
• Adds the ability to add custom links

This theme-component lacks specs, though not crucial since its only used in development, I will still be adding them later in a follow-up PR.

[keegangeorge]

Thanks @CvX 🎉 I've applied those fixes :)